Process of extracting precious metals from their ores.



A. E. VANDERCOOK.

PROCESS OF EXTRACTING PRECIOUS METALS FROIVI THEIR ORES.

APPLICATION FILED OCT. 24 1914.

Patented Sept. 12, 1916.

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ALBERT E. VANDERCOOK, 0F ALAMEDA, CALIFORNIA, ASSIGNOR 0F ONE-HALF TO LESLIE B. IVICMUR'IRY, OJE SAN FRANCISCO, CALIFORNIA.

PROCESS OF EXTRACTING PRECIOUS METALS FROM THEIR GRES.

To all whom t may concern Be it known that I, ALBERT E. VANDER- oooK, a citizen of the United States, and a resident of Alameda, county of Alameda, and State of California, have invented a certain new and useful Process of Extracting Precious Metals from Their Ores, of which the following is a specification.

rIhe invention relates to amalgamation in cyanid solution.

An object of the invention is to render amalgamation in cyanid solution practical.

Amalgamation in cyanid has been practised in several ways heretofore, but either the results obtained have been such as to discourage the use .of such step or the cost thereof has been excessive. In spite of the recognized advantages of amalgamation in removing the coarser metallic particles of gold and silver'upon which the dissolving effectof cyanid is slow, owing to the great disadvantages of the usual amalgamation practise, when crushing in solution, amalgamation is not largely practised. There is always a mechanical loss of mercury and of amalgam from the plates which finds its way into the tailings.

Another object of the invention is to provide a process by which the alkali sullids are automatically removed from the cyanid solution as quickly as they are formed or by which their formation in the solution is prevented. The sulfur of the sulfid minerals of the ores enters into solution in working-cyanid solutions and produces alkali sulfids. The deleterious effect of alkali suliids is well known. They are powerful reducing agents and cyanicides and cause the precipitation of dissolved silver, as silver sulid, and may under certain conditions re-precipitate gold and silver. In ordinary practice, soluble lead salts, such as lead acetate, are added to the solution to combine with the alkali sulds and form lead sulids, which are precipitated. This practice however, is not subject to any exact control and is governed by experience or guess, with the result that too much lor too little Soluble lead salts are Specification of Letters Patent. Pggpgegmltd @Quaid- 12, 119116 Application filed October 24, 1914.

Serial No. 868,459.

added.` rIhe results obtained are comparatively erratic.

In the present process, the alkali sulfids are removed from the solution as quickly as they form, and the sulfur is precipitated 1n the form of mercurio sulid. Mercury is, of course, always present in any amalgamatlng process, and in my process the amount of mercury which enters the solution is just suflicient to produce the desired reaction and form the insoluble mercurio sulfid, which is precipitated.

A further object of the invention is to dispose of the use of metallic copper in amalgamation practice. The deleterious action of copper on cyanid solution is well known. Its presence occasions a consumption of cyanid, a consumption of copper, a reducing action, a consumption of zinc in the precipitating apparatus or devices and the introduction of copper into the precipitates and bullion.

A further object of the invention is to provide an amalgamating process in which the mercury is maintained in a bright and active condition and-is prevented from fouling, sickening or flowering.

The invention possessesmany other advantageous features, some of which, with the foregoing, will be set forth at length in \the following description, where I shall outline in full one specific form of the process of my invention.

In the accompanying drawings I have shown one specific form of apparatus which may be employed in carrying out the process. I shall describe only one specific form of my generic invention, but it is to be un- -derstood that I do not limit myself to such form because my invention may be embodied lin a multiplicityof forms, each being a species of my said invention.

It is also to be understood that by the claims succeeding thedescription of my invention I desire to cover the invention in whatever form it may be embodied.

Referring to said drawings: Figure 1 is a vertical section of one form of apparatus with which my inventn n may be practised.

- Fig. 2 is a top or plan view of the apparatus.

` agitator, which is rotatably mounted upon the depending conductor 4. The agitator consists of the central gland orreceptacle 5 which is provided withhollow arms 6, each arm being provided with a plurality of inclined nozzles 17. The agitator is rotated by the reaction of the liquid discharg# ing from .said nozzles, and the inclination of the nozzles is such that the discharging -liquid is directed against the surface of the mercury.

The liquider slimes or pulp which is discharged from the nozzles 1s taken from the tank through the pipe 7 and forced by the centrifugal pump 8 through the pipe '9 and down through the conductor ,4. Fresh liquid or slimes carrying metallic particles to be amalgamated is fed into the tank through the pipe 12. `In order to insurethese par-- ticles being brought .into intimate contact" with the mercury and thereby hastening their amalgamation, the pipes 12 and 7 are so arranged that all material entering through pipe 12 is drawn into pipe 7 and hence is conveyed to the agitator. The ipes 7 and 12 are, preferablyqoined by a 13,

v -the third socket of which is-open, thereby allowing the liquid or slimes in the tank to' be-drawn into the pump. This arrangement causes the particles of' metal to be discharged against the mercury a plurality of times, and thereby .increases the extraction by amalgamation. The lagitation and recirculation of the solution also assists greatly in edecting the solution of the metallic particles in the cyanid solution. The tank is provided with an overflow pipe 14 for the;

value bearing cyanid solution and with adischarge pipe 15. The suction pipe 7 is preferably provided with an air cock 16, so thatwhen desirable 4air may be admitted to .the solution.` y

By -providing an iron panv to hold the mercury, all of-the deleterious effects produced; by the presence of copper are eliminated. The agitator andthe various conductors and pipeswhich are in contact ,with

V the cyanid solution are also made of iron.

When two different metals are placed t in cyanid solution, a galvanic couple is formed, and if the metals are connected by a metal- -lic conductor, -an electric current will flow' through the conductor and through the so- .the reasons why amalgamation in cyanid solution has not proved very success ul in the past. In carrying out the process of my invention I suspend the agitator above'and out of contact with the mercury, so that the galvanic couple is not completed. There is, therefore, no electric current passing through the solution, and hence the mercury 'remains bright and active.

Alkali sulids are always formed in cyanid practice when the ore contains sullid minerals and these minerals are present in a great proportion of goldand silver ores. These alkali sulids .are very deleterious and must be removed, and their removal heretofore has generally been accomplished by the addition of soluble lead salts, such as lead acetate. This lead salt combined with the alkali sulfid to produce insoluble lead suld, which precipitated. There has been no practical method of determining the proper amount of lead salts to employ in .a given working condition, and consequently too much and too little have been used. I have found that mercury is soluble in cyanid solution, producing adouble cyanid of mercury and potassium or sodium, and that the solubility is eected by the presence of oxygen, which either enters directly into the reaction or combines with evolved hydrogen,-

removing it from occlusion so that the reaction may proceed. One equation giving the reaction is as follows:

' are readily soluble inthe double cyanid, the

precious metals displacing the mercury,

' which precipitates. In practice the double cyanid appears to possess greater silver dissolving properties than the single cyanid. The double cyanid also attacks the alkali sulids as soon as they are formed or as they are forming, and causes a precipitation of the sulfur as mercurio sulfid, as

K2Hg(Cll\T) 4|K2S=HgS+4KCN. Just enough of the double cyanid is consumed as is necessary to remove the alkali sulfids from, the solution. The remaining double cyanid acts as a-solventfor the gold and silver, and precipitates mercury yas a result of the displacement of the by the gold and silver.

mercury Vserve no useful purpose.

In the present process, av slight trace of mercury is found on the zines under normal working conditions. The double cyanid of mercury and potassium or sodium performs its functions as it is formed and does not accumulate in the solution. The consumption of mercury is very slight and the cost of consumed mercury per ton of ore treated is insignificant. This process produces the amalgamation of the metallic particles of gold and silver under conditions of marked eiciency and by the solution of the mercury in cyanid forming mercuric cyanid a powerful aid in the dissolution of the gold and silver is obtained, and the alkaline sulds are desulfurized at'the moment of formation. An excess of mercuric cyanid is not deleterious since the double cyanid possesses marked dissolving properties, *taking up the gold and silver and precipitatingv the mercury. An automatic balance in the solution is maintained.

In carrying out the process, a quantity of mercury .is poured into the iron panand theV slimes or mixture of cyanid solution and ground ore is fed into the tank. When suiicient slimes have accumulatedjin the tank to submerge the pump suction pipe, the pump is started and the liquid becomes thoroughly agitated and the metallic parti- 'cles are brought into intimate and recurring contact with the mercury. Since thevagi-i tator is out of electrical contact with the mercury or with the iron pan, no current flows through the electrolyte, and hence the deleterious effect lof the current, which is present inalmost all other forms ofamalgamators, is not encountered. Due to the presence of air, either in solution or admits ted, the double cyanid of mercury and potassium or sodium is formed. The double cyanid acts as a solvent for the gold and silver and also attacks and removes the alkali sulfds. rlIhe metallic particles in the ore either become amalgamated orare dissolved by`the cyanid solution. rllhe values are recovered from the Value bearing cyanid solution in the usual mannerby precipitation and are removed from the amalgam by retortin'g or otherwise. The presence of the slight amount of mercurio cyanid in the solution as it is delivered to the precipitating e apparatus aids in the precipitation of the precious metals. Presumably the mercury forms 'a galvanic couple with the zinc, which aids the precipitation. The presence of the mercurio cyanid also retards the precipita- .tion of copper if this metal is present in the solution.

'I claim:

l. The process of recovering precious metals from a mixture of suld ore and metallic particles with a sodium or potassium cyanid solution, which consists in agitating the mixture in the presence of mercury whereby a double cyanid of mercury yand sodium or potassium is formed which removes the alkali sulids from the solution.

2. IIhe process of recovering precious metals from a mixture of sulid ore and metallic particles with a sodium or potassium cyanid solution, which consists in bringing the mixture into recurrent impinging contact with mercury and in forming in the solution a double cyanid of mercury and sodium or potassium.

3.,The process of recovering precious metals from a mixture fof sulfid ore and metallic particles with a sodium or potassium cyanid solution, which consists in agitating the mixture in the presence of mercury and oxygen whereby some of the metallic particles become amalgamated and some become dissolved by the solution.

4. The process of amalgamatingV metallic particles in a cyanid solution, which consists in directing a plurality of streams of the mixture against mercury while maintaining the stream directing means out of electrical contact with the mercury.

y 5. The process of recovering precious metals from sulfid ores containingthe same, which consists in mixing the -ground ore with cyanid solution whereby the finer metallic. particles are dissolved, bringing the mixture into contact withmetallic mercury whereby the larger metallic particles are amalgamated and whereby a double cyanid of mercury and sodium or potassium is formed which combines with the alkali sulfids formed in the solution and causes a precipitation ofthe sulfur content of the alkali sulids, separating the solution from the metallic mercury and precipitating the values in the solution.

6. rlhe process of recovering precious metals from sodium or potassium cyanid solutions containing the same in solution and in a metallic state and suld ore particles of the alkali sulfls in the solution as insoluble mercurio suld and separating the solution from the metallic mercury.

7. The process of amalgamating metallic particles in a cyanid solution containing the 10 amalgamated and a double cyanid of mercury and potassium or sodium are formed which removes the alkali sulds from the solution.

In testimonywhereof2 I have hereunto set my hand at San Francisco, California, this 15 13th day of October 1914.

ALBERT E. VANDERCOOK. In presence of- H. G. PRosT, M. L. CONTE. 

